In capacitive sensor systems, in particular capacitive approach sensors, the approach of an object towards a sensor zone substantially is measured contactless by means of generation and measurement of electric alternating fields.
Derived from the measurement signal may be functions, for example switching functions, of an electric device, in particular an electric handheld device.
For example, there exists a need to provide sensor zones of a capacitive sensor system at an electric handheld device, wherein during an approach of an object towards a sensor zone not only the approach of the object towards the sensor zone is detectable but also the position of the object relative to the sensor zone.
Depending on the position of the object relative to the sensor zone different functions may be carried out in the electric handheld device. In doing so, it is desired to achieve a preferably high position resolution. To accomplish that the capacitive sensor system may be used in different electronic devices it is further desired that the capacitive sensor system preferably is independent of the grounding state of the respective electronic device.
Known from prior art are electrode configurations, in particular for capacitive sensor systems, which function according to the so called loading method, wherein, for example for implementing a sliding controller (in a sliding controller it is important that the position of an object, for example of a finger, may be detected along the sliding controller) a plurality of sensor electrodes arranged side by side and adjacent to each other, respectively, is provided. During operation of the capacitive sensor using a loading method only one sensor electrode is required, which represents a transmitting electrode as well as a receiving electrode.
The sensor electrode is loaded with an electric alternating signal, so that an electric alternating field is emitted therefrom, wherein the capacitive load of the sensor electrode (for example by an approach of a finger towards the sensor electrode) is detected and evaluated, respectively, by means of an evaluation device. By means of the detected capacitive load it may be determined at which sensor electrode an approach of the finger has taken place.
However, such capacitive sensor systems have the disadvantage that very many electrodes are required for a high resolution (position resolution), which significantly increases the constructive effort in the manufacturing process of a sliding controller, for example. In addition, the sensor signal depends on the grounding state of the sensor electronics.
Furthermore, capacitive sensor systems are known, which also have a large number of sensor electrodes, wherein it is required for an exact detection of the position that, for example, a finger covers several sensor electrodes at the same time when contacting the sensor electrodes. Again, because of the large number of sensor electrodes required for a high position resolution the constructive effort for the manufacturing process is increased significantly.